1. Field of the Invention
The present invention relates to a mold clamping apparatus for a molding machine, a molding machine and a mold clamping method.
2. Description of the Related Art
A mold clamping apparatus of a molding machine such as a die casting machine is used to clamp a die with necessary mold clamping force for suppressing opening of the die by pressure in the die when a molten metal is injected and filled into the die. As such a mold clamping apparatus, a so-called composite type mold clamping apparatus performing an opening or closing movement of the dies and clamping the dies by using an independent actuator is known (for example, refer to Kokai (Japanese unexamined patent publication) No. H10(1998)-296739 and Kokai (Japanese unexamined patent publication) No. H8(1996)-276482).
In the compound type mold clamping apparatus, for example, a half nut is provided in a die plate holding a die and a coupled section able to mesh with the half nut is provided in a tie bar, after the coupled section of the tie bar and the half nut are meshed in a state where the dies are clamped, mold clamping force is given to the tie bar.
When changing to a new die having a different thickness to that of the old die, a positional relationship of the half nut and the coupled section of the tie bar in mold clamping changes. When a positional relationship of the half nut and the coupled section of the tie bar is changed, the half nut and the coupled section of the tie bar have possible to not be meshed, and a positional relationship of the half nut and the coupled section of the tie bar is necessary to be adjusted to a positional relationship able to be meshed. Namely, a so-called mold thickness adjustment for adjusting a positional relationship of the half nut and the coupled section of the tie bar in concert with a thickness of the die is necessary to be performed.
Meanwhile, for performing the mold thickness adjustment, a position of either of the half nut and the tie bar is necessary to be changed, and an actuator for changing a position of them becomes necessary.
However, if an actuator used only for performing the mold thickness adjustment is provided in the mold clamping apparatus, it suffers from a disadvantage that an apparatus constitution becomes complex and an apparatus cost rises.